Supporting flue structure for an electrical pulse generator

ABSTRACT

A integrated flue support construction ( 2 ) for a Marx impulse voltage generator ( 2 ) with several generator stages ( 3 ) is disclosed. It has been known to arrange a flue ( 2 ) for flushing the air of switching spark gaps ( 4 ) separately from a support frame for the switching spark gaps ( 4 ), the impulse capacitors ( 5 ) and series and parallel resistors ( 7, 8 ). According to the invention, the flue ( 2 ) has a supporting function for the switching spark gaps ( 4 ) and individual or all electrical components ( 5 - 10 ) of the impulse circuit. In one embodiment the flue ( 2 ) consists of a triangular cylinder support structure ( 2 ), wherein the side walls ( 11 ) are formed by insulating plates ( 11 ), each receiving one of the electrical components, namely the switching spark gap ( 4 ), impulse capacitor ( 5 ) and resistors ( 7, 8 ). Advantages of the invention are: a less complicated construction and a saving of costs, a more compact design with smaller flue cross section area ( 22 ) and thereby smaller self-inductance of the impulse circuit as well as easier production, transportability and handling because of stacked modules ( 14 ) each with at least one generator stage ( 3 ).

This application is a U.S. National Phase Application under 35 USC 371of International Application PCT/IB00/01945 filed Dec. 20, 2000.

TECHNICAL FIELD

The invention lies in the field of high voltage engineering, and relatesto an electrical impulse generator for generating high impulse voltagesor impulse currents, comprising a flue formed by a support structure forat least one chargeable generator stage, which comprises a switchingspark gap for generating electrical discharges in a gaseous medium andfurther electrical components for charging and/or discharging thegenerator stage, wherein the switching spark gap is arranged in the fluewith a defined gas exchange for controlling and/or keeping constant adielectric strength of the gaseous medium.

STATE OF THE ART

In a Marx impulse voltage generator several generator stages are held ontop of each other in the shape of a tower by a support frame. Thesupport frame is typically made from individual insulating tubes of hardpaper or glass fiber reinforced plastics and may comprise, for improvedmechanical stability, struts, a steel frame, intermediate platforms,lateral restraints with glass fiber cables or such. The generator stagesare charged in a parallel circuit and discharged in a series circuit byDeans of a switching member, in general a switching spark gap. Inparticular for higher impulse voltages, for the generation of which aplurality of switching members is required, spontaneous undesiredswitching must be expected when using sphere discharge gaps in free air.A reduction of the dielectric strength and a spontaneous discharge ofthe discharge gaps can be caused by contamination of the air, e.g. dueto dust deposits, floating particles, burn-off or the formation of ozonefrom previous discharges. This problem has, so far, been solved by acommon or individual housing of the discharge gaps and by leadingfiltered air through the housing.

A common housing is e.g. implemented by the company Highvolt in Dresdenby constructing a flue arranged separately and laterally from thesupport structure, which encloses the switching discharge gaps arrangedon top of each other and has an air inlet opening with a ventilator atits bottom end and an air outlet opening it its top end. The flue can bedesigned as a insulating tube and may be provided with viewing windowsfor the spark discharge gaps. The additional construction effort andcosts are disadvantageous. On the one hand, the support structure of theimpulse voltage generator must be designed for additionally holding theflue. On the other hand, the spark discharge gaps must be located, incomparison, separately from the other components of the impulsegenerator in order to guarantee sufficient insulation spacings betweenthe wall of the flue and the spark discharge gaps. The area enclosed bythe discharge circuit is thereby increased and the switching performanceis impaired by increased self-inductance.

An individual housing of each separate discharge gap is e.g. realized bythe company Passoni & Villa. Each housing is fed individually withfiltered air and an air exchange is achieved due to leaks. The roomrequired for housing each generator stage as well as the feeding tubesfor pressurized air cause again a substantial additional effort.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved electricalimpulse generator where spontaneous discharges of the discharge gaps aresuppressed with small additional effort.

The solution according to the invention consists in an electricalimpulse generator, in particular suited for generating high impulsevoltages or impulse currents, which comprises a support frame for atleast one chargeable generator stage, which comprises a switchingdischarge gap for generating electrical discharges in a gaseous mediumand further electrical components for charging and/or discharging thegenerator stage, wherein the switching discharge gap is arranged in aflue with a defined gas exchange for controlling and/or keeping constantthe dielectric strength of the gaseous medium, wherein further the flueis designed as a support structure and the support structure has asupporting function for the switching spark gap and for at least one ofthe electrical components of the at least one chargeable generatorstage. By the integration of supporting functions into the flue, theconstructive effort required for a conventional support structure can bereduced or eliminated. This allows substantial savings of costs.

In one embodiment, the flue has a supporting function for at least oneimpulse capacitor and/or at least one series resistor, parallelresistor, charge resistor and/or potential resistor of the at least onechargeable generator stage, In particular, the flue forms the supportingframe for all generator stages of the impulse generator.

In another embodiment, the flue is an insulating tube with a polygonalor round cross section and the electrical components of each generatorstage, in particular an impulse capacitor, a series resistor and aparallel resistor, can be attached to the side walls of the insulatingtube. In this manner, an interior flue is created and a very simple andcompact construction of the impulse generator is achieved.

In a further embodiment, the insulating tube has a small cross sectionarea for creating a low inductance spark current circuit with a smallenclosed area. By the integrated flue and support structure it is infact possible to lower the inductance of the discharge circuit to valuesthat have so far been unknown for housed impulse generators, and theelectrical switching characteristics can correspondingly be improved.Advantageously, the insulating tube is designed to be assembled frommodules that can be stacked on top of each other, wherein the modulescomprise at least one generator stage, preferably two, three or fourgenerator stages. The modular construction makes an efficientprefabrication at the factory possible, as well as a fast and easy finalassembly at the customer. The impulse generator can be adapted todifferent desired high voltage or high current values quickly andflexibly by adding or removing modules. The modularity is therefore alsoof great advantage to the user during operation.

In a further embodiment, the flue is built from insulating platesassembled into a triangular cylinder assembly, and each side wallcomprises mounting holes either for mounting the spark discharge gap, oran impulse capacitor or two mounting arms for receiving a seriesresistor and a parallel resistor, respectively. The triangular cylinderconstruction can be manufactured easily and has a very small enclosedinduction area of the discharge circuit.

Further embodiments, advantages and applications of the invention resultfrom the dependent claims as well as from the now following description,which makes reference to the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a supporting flue structure according to the invention foran impulse generator in cross section; and

FIG. 2 shows the flue structure of FIG. 1 in a side view.

In the figures, similar parts are designated with the same referencenumerals.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows the cross section of a generator stage 3 of an electricalimpulse generator 1 and in particular of a Marx impulse generator 1 forgenerating pulse shaped high voltages. In the shown generator stage 3there are illustrated a switching spark gap 4, an impulse capacitor 5and mounting arms 6 for snapping in at least one parallel resistor 8into generator stage 3 and at least one series resistor 7 between twogenerator stages 3 arranged on top of each other. Switching spark gap 4comprises two discharge electrodes 4 b, which are typically rounded. Thecommonly known principle of operation is based on charging the at leastone impulse capacitor 5 in several generator stages 3 in parallel viacharge resistors 9 and on discharging the capacitors via the seriesresistors 7 and the parallel resistors 8 in a series circuit in pulsedmanner. In a manner that is, per se, known, the series resistors 7, alsocalled front or damping resistors 7, serve to control the impulse risetimes and the parallel resistors 8 serve to control the impulse decaytimes. Potential resistors 9 can be present for achieving a morehomogenous voltage distribution and/or for safely removing residualcharges of the housings of the impulse capacitors 5. Impulse capacitor 5comprises lead-throughs 5 b for its high voltage terminals 5 a, whichare typically designed for 100 or 200 kV at each generator stage 3. Theterminals 5 a are connected to the terminals 4 a of the switching sparkgaps and the support arms 6 of the resistors 7, 8 in high voltage proofmanner by means of cable connections or such of minimum length. The sidewalls 11 form a support structure 2 for switching spark gap 4 and theelectrical components 5-10 of generator stage 3. In addition to this,the side walls 11 form a laterally enclosed space 22, which serves as aflue 2 for exchanging air for switching spark gap 4 located inside flue2. Air, dried air or another fluid, such as a protective gas, can be ledthrough flue 2 in order to keep the dielectric strength of switchingspark gap 4 constant or to increase it as compared to environmental air.In particular, particles floating in air, dust, burn-off or ozone ofprevious discharge processes are flushed out of the regions of theswitching spark gaps 4 by means of flue 2. Flue 2 according to theinvention therefore combines the function of a controlled air exchangeand the support function for the electrical components 5-10.

In the embodiment of FIG. 1, a particularly compact design is achievedby a triangular cylindrical flue support structure 2. The triangularshape 2 corresponds to a close or even minimum distance of switchingdischarge gap 4, an impulse capacitor 5 and the resistors 7, 8, whereinthe flat side walls 11 are especially suited for a simple mounting ofthe electrical components 5-9. Other polygonal flue cross sections 2 arepossible as well and may e.g. be useful if several impulse capacitors 5per generator stage 3 or additional auxiliary spark gaps (not shown) arepresent. Advantageously, in each generator stage 3, an impulse capacitor5, a series resistor 7, a parallel resistor 8 and/or a dischargeresistor 9 are arranged outside flue 2 and comprise contacts orlead-throughs 5 b into the interior of flue 22. In this manner, theelectrical components 5-9 and in particular the resistors 7-9 can beexchanged very easily and are well visible from the outside. Inparticular, the value of the resistors can by checked due to acharacteristic coloring. A drive 4 d for adjusting the switching sparkgaps 4 can be arranged in flue 2. Flue 2 can be provided with viewingwindows 4 c for the witching spark gaps 4, which serve, in a per-seknown manner, for visual control and, where applicable, for an opticalsynchronization and thereby easier firing of the air in switching sparkgap 4. By means of the presented triangular cylinder design 2 a pulsewave or discharge current circuit of very small cross section orenclosed section 22 and therefore low self induction can be achieved.

With the integration flue support structure 2 with an internal flueinterior 22 a support structure 2 is created that is very stable,compact, easy to manufacture and easy to handle, for several or allgenerator stages 3 of an impulse generator 1. Impulse generator 1 canalso be an impulse current generator 1 built in similar manner.Conventional support structures with support tubes and steel frame orintermediate connecting plates for laterally mounting the support tubescan therefore be simplified or, as shown, be dispensed with completely.The flue support structure 2 can, where applicable, be further laterallystabilized by lateral bracing with glass fiber cables or such.

In the given embodiment the triangular cylinder construction 2, i.e. thetube or hollow cylinder 2 with triangular cross section, is built frominsulating plates forming the side walls 11, which comprise mountingholes for mounting the electrical components 4-9. The insulating plates11 are joined by metallic bracket members 11 a contacting adjacentterminals 4 a, 5 a, 6 a of the electrical components 4-9 via leads 11 bor similar. Two side walls 11 of the triangular cylinder construction 2comprise, in the region of the impulse capacitor 5, projecting parts 12,each having at least one support hole 13. In particular, a connectingline through the support holes 13 runs substantially through a center ofmass of the impulse generator 1 such that the impulse generator 1 or anindividual generator module 14 can be lifted and transported very easilyand without lateral tiling by means of a lifting tool engaging thesupport holes.

FIG. 2 shows the flue support structure 2 in a lateral view. Thetriangular, polygonal or round insulating tube 11 is shown to beassembled from modules 14 stacked on top of each other. In the case oftriangular cylinder modules 14, for example, stackability can beimplemented by providing the cylinder modules 14 with projectingcentering members (not shown) arranged in staggered relation to a sidewall 11, in particular by centering pins glued or mounted to the bracketmembers 11 a. In general, a centering frame for stacking the cylindricalmodules 14 can be present as well. Each module 14 comprises at lest onegenerator stage 3 and preferably two, three or four generator stages 3.Cylinder modules 14 can also be used with arbitrary other flue crosssection geometries. The bottommost module 14 should have an air entryopening 15 a with a ventilator and the topmost module 14 an air exitopening 15 b. Air entry and air exit can also be exchanged. The supportstructure and the flue 2, in particular a flue 2 forming the supportstructure, can also be mounted on a displaceable frame 16, in particularon a wheeled vehicle or an air-cushioned vehicle.

1. An electrical impulse generator for generating high impulse voltagesor impulse currents, comprising: a flue formed by a support structurefor at least one chargeable generator stage, which comprises a switchingspark gap for generating electrical discharges in a gaseous medium andfurther electrical components for charging and/or discharging thegenerator stage, wherein the switching spark gap is arranged in the fluewith a defined gas exchange for controlling and/or keeping constant adielectric strength of the gaseous medium, wherein the support structurehas a supporting function for the switching spark gap and for at leastone of the electrical components of the at least one chargeablegenerator stage, and wherein the support structure comprises aninsulating tube formed by a plurality of side walls so as to have apolygonal or round cross section, wherein an impulse capacitor, a seriesresistor, a parallel resistor and a charge resistor are arranged, foreach generator stage, outside the flue on an outer side of the sidewalls of the insulating tube, wherein the flue further comprisescontacts or lead-throughs into an interior of the flue, wherein each ofthe side walls comprises mounting holes for either mounting one of: theswitching spark gap, the impulse capacitor, and two mounting arms forreceiving the series resistor and the parallel resistor, and wherein twoof the side walls of the insulating tube comprise projecting parts,wherein the impulse capacitor of each stage is arranged between saidprojecting parts, and wherein each projecting part has at least onesupport hole adjacent to said impulse capacitor.
 2. The electricalimpulse generator of claim 1, wherein a connecting line through thesupport holes runs substantially through a center of mass of the impulsegenerator.
 3. The electrical impulse generator of claim 1, wherein theside walls of the insulating tube comprise insulating plates assembledinto a triangular cylinder assembly.
 4. The electrical impulse generatorof claim 2, wherein the side walls of the insulating tube compriseinsulating plates assembled into a triangular cylinder assembly.
 5. Theelectrical impulse generator of claim 1, wherein the insulating tubecomprises modules stackable on top of each other, each module comprisingat least one generator stage.
 6. The electrical impulse generator ofclaim 1, wherein terminals of the switching spark gap, the impulsecapacitor, the series resistor and the parallel resistor are arrangedinside the flue.
 7. The electrical impulse generator of claim 1, whereinthe side walls of the insulating tube comprise insulating plates linkedby metallic bracket members contacting adjacent terminals of theswitching spark gap and the electrical components.
 8. The electricalimpulse generator of claim 1, wherein the flue comprises viewing windowsfor the switching spark gaps.
 9. The electrical impulse generator ofclaim 1, wherein the flue comprises at a first end an air input openingwith a ventilator and at a second end an air outlet opening.
 10. Theelectrical impulse generator of claim 1, wherein a plurality ofgenerator stages are provided, and the flue supports all generatorstages of the impulse generator.
 11. The electrical impulse generator ofclaim 1, wherein the insulating tube comprises a plurality of stackablemodules, each module carrying two to four generator stages.
 12. Theelectrical impulse generator of claim 1, wherein the flue comprises aplurality of modules stacked on top of each other, each module beingformed by a plurality of insulating plates and carrying at least onegenerator stage, and wherein each module comprises projecting centeringmembers in staggered relation to the insulating plates.
 13. Theelectrical impulse generator of claim 1, wherein the flue comprises aplurality of modules stacked on top of each other, each module beingformed by a plurality of insulating plates and carrying at least onegenerator stage, and wherein each module comprises a centering frame forstacking the modules.
 14. The electrical impulse generator of claim 1,further comprising a drive for the switching spark gap, the drive beingarranged in the flue.
 15. The electrical impulse generator of claim 1,further comprising further spark gaps in addition to the switching sparkgap, and wherein said further spark gaps are also arranged in the flue.16. The electrical impulse generator of claim 1, wherein the supportstructure and the flue are arranged on a displaceable vehicle.
 17. Theelectrical impulse generator of claim 1, wherein the impulse generatorcomprises a Marx impulse voltage generator or an impulse currentgenerator.
 18. An electrical impulse generator for generating highimpulse voltages or impulse currents, comprising: a plurality ofchargeable generator stages, each generator stage having a switchingspark gap for generating electrical discharges in a gaseous medium forcharging and/or discharging the generator stage, and an impulsecapacitor, a flue formed by a plurality of side walls and having apolygonal or round interior space with a defined gas exchange forcontrolling and/or keeping constant a dielectric strength of the gaseousmedium, wherein, of the side walls of the flue, first and second sidewalls comprise projecting parts extending over a third wall, whereinsaid switching spark gaps are supported by said flue and are arranged insaid polygonal or round interior space, and wherein said impulsecapacitors are supported by and arranged outside of said third side wallbetween said projections of said first and second side walls.
 19. Theelectrical impulse generator of claim 18, wherein said projectionscomprise support holes adjacent to said impulse capacitors.
 20. Theelectrical impulse generator of claim 18, wherein the flue is formed bythe first, second and third side walls and has a triangular interiorspace.
 21. The electrical impulse generator of claim 19, wherein theflue is formed by the first, second and third side walls and has atriangular interior space.